Method of treating fibrous material utilizing a radio-frequency field which extends predominantly at right angles to the length of said material



Dec. 23, 1958 c. A. BAER 2,865,

METHOD OF TREATING FIBROUS MATERIAL UTILIZING A RADIO-FREQUENCY FIELD WHICH EXTENDS PREDOMINANTLY AT RIGHT ANGLES TO THE LENGTH OF SAID MATERIAL Filed Aug. 19, 1955 3 Sheets-Sheet 1 INVENTOR.

BY Car/ ,4. Boer ATTORNEY Dec. 23, 1958 c. A. BAER 2,865,790 METHOD OF TREATING FIBROUS MATERIAL JTILIZING A RADIO-FREQUENCY FIELD WHICH EXTENDS PREDOMINANTLY AT RIGHT A GLES TO THE LENGTH OF SAID MATERIAL FilOd Aug. 19, 1955 I 3 Sheets-Sheet 2 ELECTRODE INVENTOR.

Car/ A Baer METHOD OF TREAT A RADIO-FRE Dec. 23, c. A. BAER 2,86

ING FIBROUS MATERIAL UTILIZING QuENcy FIELD WHICH EXTENDS PREDOMINANTLY AT RIGHT ANGLES To THE LENGTH OF SAID MATERIAL 3 Sheets-Sheet 3 Filed Aug. 19, 1955 INVENTOR. Car/ A 509/ Y A TTO/FNEY United States Patent METHOD OF TREATING F IBROUS MATERIAL UTILIZING A RADIO-FREQUENCY FIELD WHICH EXTENDS PRED'OMIYANTLY AT RIGHT ANGLES TO THE LENGTH OF SAID MATERIAL Carl A. Baer, Washington, D. C.

Application August 19, 1955, Serial No. 529,452

2 Claims. (c1. 117-9s This invention relates to the impregnating and bonding of fibrous materials of all kinds, either natural or synthetic, in order to improvethe tensile strength of the finished product, and thus enhance its utility; and it is equally applicable to unwoven or woven materials. That is to say, the invention is applicable to continuous fibrous sheets using either natu.al, synthetic, or any combinations of such fibers, made up of multiple film-.ike layers in natural tension, interlocking to form a homogeneous sne-t, produced directly from cards, drawing frames, combing machines or garnets, or other equipment. it is also applicable to strands and cords produced on spinning machinery or produced directly from intermediate machines, such as fly frames; as well as to unwoven or woven fabrics that may be treated under tension.

In the production of fibrous materials of the types referred to hereinbefore, it has long been the practice to treat the material with various bond rig SOlLllllLIlS and .then dry itunder heat created either by sleam cr banks of infra-red lamps. Due to the inherent viscosity of the liquid, as well as its surface tensicn, the bonding solutions employed preliminary to such steam or infra-red heating steps do not spread thoroughly around the fi-ers or into, and through, the interstices formed by the mass of fibers.

Viscosity or internal fluid friction is, of course, the internal frictional resistance offered by a fluid to change of shape or to relative motion of its parts.

I have discovered that, when treated in a manner which will be referred to hereinafter, such bonding solutions may be made to permeate all the interstices of the fibrous mass and coat completely the available fiber surfaces, producing thorough adsorption to all such fiber surfaces, and setting the bonding material in position with the result that the finished products are of vastly improved tensile strength and, accordingly, utility.

As well be understood by those skilled in the art, adsorption is the adhesion of molecules of subsances in solution to the surface of a solid resulting in greater concentration at such a surface.

More particularly, I have discovered that, when fibrous materials of various types are'treated with appropriate bonding solutions (whether applied by spraying or immersion) and then exposed to a radio frequency field between two electrodes, the polar reversal of this radio frequency field (which may, for example, utilize between five and three thousand million cycles per second) rotates the molecules of the bonding solution which breaks down the surrounding elastic film tensin and viscosity of the solution. The radio frequency field (l) accelerate the molecules of the solution to interpene'rate and permeate any and all crevices and interstices in the mass cf fi'ters and to coat all available fiber surfaces, producing thorough adsorption thereof resulting in a more complete impregnation; and (2) the molecular reversal simultaneously produces a cumulative heating action uniformly thrcughoutthe material thatsets the impregnating binder "ice in place to a solid consistency, thus increasing the relative tensile strength of the fibrous products so treated.

The invention, then, comprises the features hereinafter fully described and as particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative em.'odiments of the invention, these being indicative of but several of a number of ways in which the principles of the invention may be employed.

In said drawings:

Figure 1 is an enlarged, transverse, sectional view illustrating schematically the maner in which a thermopla;tic bonding solution normally reacts when placed in contact with a mass of fibers, such as cotton fibers;

Figure 2 is a schematic side elevational view of a layout of apparatus which may be successfully employed to practice the teachings of the present invention;

Figure 3 is a diagram of an electrical circuit which may be employed to create a satisfactory radio frequency field between the elactrodes of the apparatus;

Figure 4 is an elevational view illustrating the application of the teachings of the present invention to the wellknown ring spinning process for yarn; and

Figure 5 is a view similar to that of Figure 2, but disclosing the apparatus as applied to a built-up fabric of the type which is used in the manufacture of tire casings.

Referring more particularly to the drawings, the numeral 1 designates, in Figure 1, a thermcplasic bonding solution as applied to a mass of cotton fibers 2 in accodance with prior art practices. It will be observed that, in Figure 1, the bonding solution 1 makes ccnt;ct with only a relatively small area of the fibers, due to its visccsity and surface tension; that is, it is unable to spread thoroughly around the fibers and penetrate into, and through, all of the interstices within the mazs of fibers. As will appear more fully hereinafter, the practice of the teachings of the present invention will eliminate the condition illustrated in Figure 1 and produce a thorough penetration of all interstices and thorough adsorption of fiber surfaces with resulting increase in the bonding strength of the fibers to each other.

In the lay-out of Figure 2, I have illustrated a series of instrumentalities which may successfully be utilized to practice the teachings of the present invention on various unwoven fibrous materials; and, specifically, carded fibers. According to this embodiment, three (3) card cylinders 3, 4 and 5 discharge from doffers 6, 7 and 8, respectively, producing films, as shown at 9, 10 and 11. These films 9, 10 and 11 successively superimpose in the manner shown; and move upon an endless belt 12 into an impregnating tank 13.

As the tops of the films 9, 10 and 11 leave the doffers 6, 7 and 8, respectively, they are preferably curved over smooth brass pipes 14, 15 and 16 which are so perforated that very light air currentspass through the perforations and cause the sheets to practically float thereover. This passage of air increases, as desired, the tendency of the fibers to protrude upwardly from the top surface of the film; so that, as the particular film descends and is superimposed upon the film therebelow, it joins and interlocks with this lower film. Where the films 9, 10 and 11 move onto the endless belt 12, with the film 10 overlying the film 9, and the film 11 overlying the film 10, they pass into position over smooth pipes 17, 18 and 19, in the order indicated. If it is desired to increase the transverse laying of fibers, then by having holes in the pipes at varying angles from the direction of movement of the endless belt 12, the air currents may be directed in transverse angles so as to gently aid transverse location of the fibers.

When the top of the endless conveyor belt moves over its supporting rolls, there is permitted a certain amount of play, whereby the belt is not fiat at its top surface, but effects a hump where it presses upon these supporting rolls. The immediately aforementioned condition additionally works the sheet of films, and contributes toward its homogeneity. As the sheet moves into the impregnating tank, any type of impregnation (dipping or spraying) may be utilized.

Of course, the cards and equipment described above may be substituted by any suitable machine that produces a continuous, uniform, non-woven web with random orientation of fibers and relatively even selvage over a wide range of fibers and thickness of webs.

The bonding solutions in the process of the present invention may be considerably varied, depending upon the fibers employed and the product to be made. There may be employed all thermoplastic solutions or liquids of polyethylene, rubber hydrochloride, chlorinated rubber, alkyd resins, phenol aldehyde resins, vinyl acetate, polyvinyl chloride, vinylidene chloride, cellulose deriva tives such as cellulose esters and cellulose ethers when properly plasticized with selected plasticizers in suitable amounts, copolymers of butadiene and styrene known as Synthetic Rubber GRS, polystyrenes, nitrocellulose properly plasti'cized with selected plasticizers so as to be suitably thermoplastic, inert protein polymer known as Zein properly formulated and plasticized, and other generally similar compositions of materials; also starch, zinc chloride, sulphur zincate, phenol formaldehyde, sulphuric acid, sodium hydroxide, polyvinyl alcohol, and rubber latex.

These bonding materials may be used with selected plasticizers or wetting agents, or any variety of compounding ingredients, while latex may be used with or without vulcanizing ingredients. There is no limit to the bonding liquids which can be developed for binding materials depending upon the fibers used and the purpose of the ultimate sheet or cord.

As the impregnated sheet rises from the impregnating tank 13, it moves through rolls 20 and 21 which squeeze out excess bonding solution. The impregnated sheet may then be passed between metallic rolls 22 and 23 which are connected as electrodes so as to produce a radio frequency field therebetween. As these metallic rolls 22 and 23 press against the sheet, they lightly squeeze the bonding solution throughout the mass of fibers. In addition, I have discovered that the molecular reversal and friction created by the radio frequency field when passed across said fibrous sheet is most effective in forcing the bonding solution within all of the interstices between the fibers and thoroughly coating them in such manner as to produce complete adsorption; and the heat sets the binder in place in the sheet. Then, as the sheet moves up between the electrodes 24 and 25, it is subjected to a further radio frequency field which by its cumulative heating of the bonding material produces a uniform drying action throughout the sheet. As the sheet leaves the electrodes, if additional heat is needed, it moves through an infrared lamp oven 26 which finishes the drying operation, and the dried sheet 27 is thereupon rolled up in finished form.

It will, of course, be understood by those skilled in the art that, whenever the bonding solution contains Water in any form, the metal surfaces of the electrodes between which the sheet passes should be covered by a suitable insulation, such as porcelain, or insulated by a uniform coating of Bakelite or thin mica sheets, as described in my Patent No. 2,691,613, dated October 12, 1954. As explained in this patent (col. 8 of the specification, line 11 et sequeta) this may be done by a uniform coating of Bakelite or thin mica sheets over the contacting surfaces of the electrodes either of which may be securely adhered to the metal electrodes by means of an adhesive such as Cyclo-weld. In the case of Bakelite, the metal electrodes may first be coated with a thin layer of Cyclo-weld and then heated to 100 degrees C. Then, a thin coating of Bakelite may be applied over the coating of Cyclo-weld,

4 after which it may be baked at a temperature of 300 degrees 0., thus producing a thin smooth durable coating that will adhere firmly to the metal electrode and insulate the contacting surface from the electrically-conductive wet sheet.

As stated hereinbefore, Figure 3 is a circuit diagram of a satisfactory circuit arrangement whereby the radio frequency field may be created between the electrodes of the apparatus. If the power load is heavy, additional condensers may be added, as shown by the dotted lines. However, the circuit arrangement may be varied as desired to secure the proper radio frequency action necessay.

In radio frequency heating, the power requirement is determined in accordance with the equation P=17.6 SwDT/t S is specific heat of the substance being heated; w is weight of the substance in pounds; DT is the temperature change in degrees F.; t is the heating time in minutes; and P is the power requirements in watts.

After the required power is calculated from this, and the capacity of the load estimated, the operating frequency can be determined at which the voltage across the load will not cause flash-over.

This is outlined to illustrate that the amount of electric power required to complete the bonding and drying action is dependent upon the weight of the impregnated sheet and the speed at which it passes between the electrodes. Where the weight and speed of the sheet would create excessive power demands, it is practical to supplement the drying by the use of either infra-red ray lamps, steam, etc.

The sheets to be treated may be of thicknesses from 4 mils up, depending upon the number of machines and the number of layers to be made, and may be used for numerous industrial purposes, including base for coated fabric, masking tape, shoe fabrics, window shade materials, sheet insulation, non-slip rug cushions, fused collar linings, imitation rice papers, tire fabrics, base for flat industrial belting, window display fabrics, pipe coverings, filters, coat interliners, wallpaper, leatherette, electrical insulation, industrial belting, and application to plastic laminates.

According to the teachings of the present invention, there need be practically no limit to the variety of fibers to be treated; either throughout a given sheet, or varied in different layers of a given sheet. For example,- cotton may be mixed with glass fiber wherein the glass is needed for high temperatures, the cotton being used as a carrier until the finished sheet is in place.

There are a variety ofways for varying the longitudinal or transverse strength of such a sheet. In the normal carding operation, the operator is concerned with producing fibers in a web in longitudinal direction. This can be secured by: 1) the type, grinding and adjustment of wires on card cylinder flats and dotfer; (2) mechanical device for increasing the speed of the fly comb in relation to surface speed of doffer; (3) adding sufficient moisture so that fibers remain in parallel position on cylinder and doffer wires; (4) increasing the feed under the above conditions adds to the number of parallel fibers in a longitudinal direction.

It is apparent that the above methods of producing fibers in a longitudinal direction in the web, if reversed, will produce a greater percentage of fiber in a transverse direction.

There are various ways in which the fibers can be placed in a transverse direction; and, in fact, machinery is now in use which allows a continuous cross-laying of alternate webs in the lap.

My improved technique may be successfully applied to yarns and rovingsmade of a twisted sheet strip, as well as to sheets of traditionally spun cords, such as are used in tire fabrics.

In Figure 4, I have disclosed the application of the teachings of the presentinvention to the standard ring asearob spinning processes. According to this embodiment, electrodes 29 and 30 are disposed where the yarn passes from the rolls to the porcelain thread guide 31, and thence to the spindle 37. The last two rolls 32 and 33 may be utilized to obtain the impregnation of the yarn 34 by having the lower roll 33 pick up the bonding solution from a transfer roll 35 which is partially immersed in an impregnating bath 36. In passing from these rolls 32 and 33 to the thread guide 31, the impregnated yarn is directed between the electrodes 29 and 30 and through the radio frequency field which is established thereby. As the impregnated yarn is twisted and stretched, the bonding agent is so actuated by the radio frequency field applied across said yarn that the molecular reversal produces complete adsorption which, together with the cumulative heating action of said field, thoroughly coats, sets, dries and bonds the twisted fibers of the yarn in the manner of the carded fibers of Figure 2.

An adaptation of the mule spinning frame can be used not only to spin impregnated yarns, but the bonded unwoven sheet itself may pass through rolling knives and be cut in strips approximately one-half or three-quarters of an inch in width, or as desired, and wound in spools; and these spools may then be placed upon an adaptation of the mule spinning frame; and this flat sliver may then be dipped into a bonding solution, twisted, and then passed onto the cop of the mule spinning frame, whereby this flat sliver would be twisted so as to form a cord with the bonding material concentrated into a central core. This, then, would be passed through the radio frequency field across said cord, whereby it would be more thoroughly impregnated (i. e., complete adsorption), set, dried and bonded as a twisted cord. This product would have great strength and utility.

In Figure 5, I have illustrated the application of the discoveries of the present invention to a built-up fabric of the type which is used in the manufacture of tire casings. It is well known that, due to the stress under which fabrics of this type must operate, the cords should be prestretched before they are set in latex compound and cured; and the more thorough the impregnation, and the more strength that can be created with any given bonding solution used, the greater the strength of the built-up fabric, which is of great importance as it adds to the safety of the finished tire in use.

As shown in Figure 5, the fabric 38 is unwound from a roll 39 and is stretched in a longitudinal direction between spaced pairs of rolls 40 and 42, heat being provided by a pair of intermediately disposed heating rolls 41. After leaving the rolls 42, the fabric 38 is directed around a roll 43 which is immersed in a bath of latex compound. After being immersed in the bath of latex compound, the fabric should be dried so that the latex compound will set in the fiber sheet, giving it both set and strength. According to the present invention, the woven or built-up fabric 38, after impregnation, rises from the bath and is passed between rolls 44 which are, in effect, radio frequency electrodes producing a radio frequency field applied across the fiber sheet therebetween; and the action of the rolls in squeezing the bonding material through the fabric will be enhanced by the action of the radio frequency field which, due to the molecular reversal explained hereinbefore, nullifies the viscosity of the bonding material and causes it to penetrate all of the interstices of the fabric and thoroughly coat all available fiber surfaces thereof by complete adsorption; also the molecular friction sets the bonding material in position, adding to the inherent strength of the fabric as a whole.

With such fabrics, it may be desirable to have the electrodes placed as shown at 45, rather than utilizing rolls 44 as electrodes which can be used instead to squeeze out excess bonding solution. In such instance, the drying of the fabric sheet, which was initiated by the electrodes 45, may be completed by passing it through an infra-red lamp oven 46 or steam oven, and from there, to the finished roll d7.

Similarly, in utilizing the process previously described in connection with the apparatus illustrated in Figure 2 (for the non-woven sheet), rolls 22 and 23 need not be electrodes, but may be used instead to squeeze out excess bonding solution, or omitted; whereupon the action of electrodes 24 and 25 will produce adsorption and at least initially set the binder in place with the drying completed by the infra-red lamp oven 26, as above described for the woven sheet.

It will be understood that, in the apparatus of Figure 5, the fabric 33 is constantly maintained in tension. Accordingly, the radio frequency action upon the stretched and impregnated fabric, combined with the uniform heating throughout the fabric, considerably .increases the tensile strength of the finished fabric.

It will be observed that, in each of the illustrative embodiments described herein, and illustrated in the accompanying drawings, the application of the radio frequency field is across the fibrous material being treated; and this enables the attainment of the complete adsorption or interpenetration and coating referred to. As used herein the term across is intended to mean intersect or pass at an angle especially a right angle (see Websters New International Dictionary, 2nd edition, unabridged).

The term fibrous material as used in the appended claims is intended to cover materials which are either woven or unwoven, and which may be in any form, such as fibrous sheets, cords, yarns, etc.; and whether processed with or without tension.

While I have shown and described certain specific embodiments of the present invention, it will be readily understood by those skilled in the art that I do not wish to be limited exactly thereto, since various modifications may be made without departing from the scope of the invention as defined in the appended claims.

I claim:

1. The method of treating fibrous material which includes applying thereto a sufiicient quantity of bonding solution to mechanically impregnate the fibers throughout; and immediately applying to the fibrous material over a substantial area thereof a radio-frequency field which extends predominantly at right angles to the largest surface of said material to thereby create such a uniform field which will cause the solution binder solids to become fluid to the extent of practically nullifying the viscosity of said binder solids uniformly throughout whereupon said field will force them into the interstices between the fibers to the extent of producing substantially complete interpenetration and adsorption of all available fiber surfaces uniformly, thus completing and perfecting any aforementioned mechanical impregnation before the setting of the binder of the solution, and then, by the cumulative uniform heating action of said field upon the fibrous mass, creating sufiicient heat to at least initially set the binder in place in the fibrous mass; whereby, when dry, the tensile strength of the fibrous mass is increased ovcr that which would be obtained by any mechanical impregnation and subsequent drying without the use of the aforementioned specifically applied radio frequency field.

2. The method of treating fibrous material which includes applying thereto a sufiicient quantity of bonding solution to mechanically impregnate the fibers throughout; and immediately applying to the fibrous material over a substantial area thereof a radio-frequency field which extends predominantly! at right angles to the largest surface of said material to thereby create such a uniform field which will cause the solution binder solids to become fluid to the extent of practically nullifying the viscosity of said binder solids uniformly throughout whereupon said field will force them into the interstices between the fibers to the extent of producing substantially complete interpenetration and adsorption of all available fiber surfaces uniformly, thus completing and perfecting any aforementioned mechanical impregnation bethe setting of the binder of the solution, and then, cumulative uniform heating action of said field n the fibrous mass, creating sufiicient heat to at least .ly set the binder in place in the fibrous mass, and ter subjecting the fibrous mass to supplemental ods of heating; whereby, when dry, the tensile ngth of the fibrous material is increased over that 'hieli wculd be obtained by any mechanical impregnau 1 and subsequent drying without the use of the aforeri urfiilfid specifically applied radio-frequency field.

fore

References Cited in the file of this patent UNITED STATES PATENTS Hsu July 30, Wilson -s Aug. 6, Story Apr. 11, Kopp Nov. 27, Arnold July 20, 

1. THE METHOD OF TREATING FIBROUS MATERIAL WHICH INCLUDES APPLYING THERETO A SUFFICIENT QUANTITY OF BONDING SOLUTION TO MECHANICALLY IMPREGNATE THE FIBERS THROUGHOUT; AND IMMEDIATELY APPLYING TO THE FIBROUS MATERIAL OVER A SUBSTANTIAL AREA THEREOF A RADIO-FREQUENCY FIELD WHICH EXTENDS PREDOMINANTLY AT RIGHT ANGLES TO THE LARGEST SURFACE OF SAID MATERIAL TO THEREBY CREATE SUCH A UNIFORM FIELD WHICH WILL CAUSE THE SOLUTION BINDER SOLIDS TO BECOME FLUID TO THE EXTENT OF PRACTICALLY NULLIFYING THE VISCOSITY OF SAID BINDER SOLIDS UNIFORMLY THROUGHOUT WHEREUPON SAID FIELD WILL FORCE THEM INTO THE INTERSTICES BETWEEN THE FIBERS TO THE EXTENT OF PRODUCING SUBSTANTIALLY COMPLETE INTERPENETRATION AND ADSORPTION OF ALL AVAILABLE FIBER SURFACES UNIFORMLY, THUS COMPLETING AND PERFECTING ANY AFOREMENTIONED MECHANICAL IMPREGNATION BEFORE THE SETTING OF THE BINDER OF THE SOLUTION, AND THEN, BY THE CUMULATIVE UNIFORM HEATING ACTION OF SAID FIELD UPON LY SET THE BINDER IN PLACE IN THE FIBROUS MASS; WHEREBY WHEN DRY, THE TENSILE STRENGTH OF THE FIBROUS MASS IS INCREASED OVER THAT WHICH WOULD BE OBTAINED BY ANY MECHANICAL IMPREGNATION AND SUBSEQUENT DRYING WITHOUT THE USE OF THE AFOREMENTIONED SPECIFICALLY APPLIED RADIOFREQUENCY FIELD. 